1. Field of the Invention
The present invention relates to an internal combustion engine operating method in which, to obtain motive power, an internal combustion engine is driven by burning a mixed fuel in a combustion chamber thereof and a fuel supply system for supplying a mixed fuel to a combustion chamber of an internal combustion engine.
2. Description of Background Art
Out of growing concern about environmental problems, use of a mixed fuel of gasoline and ethanol as a fuel for gasoline engines (internal combustion engines) mounted on automobiles is being studied. When a gasoline engine is operated using the mixed fuel, the amounts of carbon monoxide, hydrocarbon, and nitrogen oxide (NOx) contained in the exhaust gas of the gasoline engine are remarkably reduced compared with when the gasoline engine is operated using gasoline only. In addition, with ethanol being a substance which is decomposed naturally, the burden on the environment is largely reduced. In cases where so-called biomass ethanol produced by fermenting, for example, sugarcane or corn is burned, the carbon dioxide that had been captured by the sugarcane or corn is merely released back into the atmosphere, so that no additional carbon dioxide is emitted. Besides, since ethanol is cheaper than gasoline, the cost of engine operation is reduced.
What is described above concerns gasoline engines. For diesel engines which use light oil, too, reducing the amount of NOx in exhaust gas is demanded. Based on this standpoint, use of an emulsion fuel prepared by adding an emulsifying agent to light oil to distribute water in the light oil has been proposed (see, for example, JP-A No. 2004-68666 and JP-A No. H07-501373). It is considered that, when such an emulsion fuel is burned in a combustion chamber, the evaporative latent heat of water lowers the combustion temperature in the combustion chamber resulting in reduced NOx generation.
Referring to JP-A No. 2004-68666 and JP-A No. H07-501373, it is considered that using an ethanol-gasoline mixed fuel added to by water for a gasoline engine also lowers the combustion temperature and further reduces NOx generation. Mixing the mixed fuel containing ethanol accounting for 10% by volume with water in an amount equivalent to 1% by volume of the mixed fuel, however, causes phase separation between the gasoline and water and, as a result, most of the ethanol is transformed into an aqueous phase. This changes gasoline properties, for example, octane number and distillation characteristics.
Thus, operating a gasoline engine using a mixed fuel of gasoline and water involves great difficulty. In view of this situation, it is generally considered that water should not be allowed to mix in with gasoline.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an internal combustion engine operating method in which a mixed fuel of water and gasoline can be burned and a fuel supply system for supplying the mixed fuel to a combustion chamber of the internal combustion engine.